Sparking plug



Patented Sept. 13, 1938 UNITED STATES PATENT OFFICE Application March 3, 1937, Serial No. 128,851 In Great Britain March 3, 1936 1 Claim.

This invention relates to improvements in sparking plugs for internal combustion engines, and more particularly to sparking plugs in which a heating resistance element adapted for connection to a low tension battery is incorporated with the plug for the purpose of heating the sparking plug and driving off condensation products and facilitating ignition. The present invention has for an object an improved construction of sparking plug of this type.

In accordance with the invention, a sparking plug comprises in combination with a plug body a central electrode, said central electrode having a lower free end extending within said plug body, a conducting sleeve surrounding and insulated from said central electrode, a conducting bush surrounding and insulated from said conducting sleeve, a gland nut engageable with said bush to hold said bush in said plug body, a resistance coil disposed around and spaced from the lower free end of said central electrode, said resistance coil being adapted to be heated from a source of low tension current, the resistance coil being connected at one end to said conducting sleeve and at the other to said bush and means remote from the plug body providing connection between said conducting sleeve and the source of low tension current.

The single figure oi the accompanying drawing shows in cross section a sparking plug constructed in accordance with the present invention.

Referring now to the drawing, I denotes the tubular plug body, and 2 the central or main electrode.

The shank of the central electrode 2 is surrounded over the major portion of its length by an insulating sleeve 4 embraced by a metal conducting sleeve II to which is attached between the fixed nut I and the locking nut I5, a low tension conductor I2. The high tension conductor 8 is clamped to the central electrode 2 by means of a fixed nut I II and a locking nut I8. Suitable insulating members I! and II are mounted under 45 the fixed nuts I and It, respectively. The conductors 9 and I 2 may be led to any convenient source of electric current such as a battery (not shown), the current being controlled from any convenient position such as the dash-board of a car. The sleeve I I is surrounded by insulation I3 embraced by a flanged conducting bush J engaged 5 by the gland nut 6, threaded into the plug body I. To the inner end of the sleeve II is attached one end of a resistance coil element 8a surrounding the inner end portion of the central electrode 2 within the pocket I so that, when the sparking 1o plug is in use, combustible gases may enter the pocket 1 and be ignited by the coil 8a in the event of failure of the sparking plug to ignite such gases. I4 denotes the earthed electrodes of the plug. The resistor coil 8a is earthed by connec- 1 tion to the bush 5.

As will be clear, the resistor coil to in the position shown serves not only to maintain the plug points free from moisture and to heat up the plug in order to facilitate starting, but serves also as a preheater for the combustible gases entering the pocket I.

The resistor coil 8a, while being exposed to the combustion gases, is shielded by the plug body I from fuel spray when used in engines operating under so-called solid-injection fuel systems.

I claim:

A sparking plug comprising in combination with a plug body, a central electrode, said central electrode having a lower i'ree end extending within said plug body, a conducting sleeve surrounding and insulated from said central electrode, a conducting bush surrounding and insulated from said conducting sleeve, a gland nut engageable with said bush to hold saidbush in said plug body, a resistance coil disposed around and spaced from the lower free end of said central electrode, said resistance coil being adapted to be heated from a source of low tension current, the resistance coil being connected at one end to said conducting sleeve and at the other to said bush and means remote from .the plug body providing connection between said connecting sleeve and the source of low tension current.

WILLIAM JOHN VINCENT. u 

